1. Field of the Invention
The present invention relates to an optical scanning apparatus to be used, for example, in a bar code reader. Moreover, the present invention relates to an optical reader, and particularly to a bar code reader called a multi-head scanner.
2. Description of the Related Art
Recently, point-of-sale (“POS”) systems have gained widespread use, in which checkout can be conducted by reading bar code information attached to a commodity. In such a POS system, the bar code information is input by scanning the commodity and the checkout can be conducted on the basis of such information. Therefore, the workload of the checkout operator can be reduced.
In the POS system, a stationary scanner, which is installed in the checkout counter, is mainly used.
Up to now, a bar code scanner having a single reading window from which a scanning pattern is emitted has been mainly used to scan a bar code. The reading window can be installed in the horizontal direction to the counter surface or installed in the vertical direction thereto. However, in the case of such apparatus, the direction in which the bar code (direction of bar code) can be read is limited and, therefore, an operator has to direct the bar code toward the reading. This has been a problem for the operator.
In order to reduce this problem, a so-called multi-head scanner is now widely used. This scanner is provided both with a window which is parallel to the counter surface (bottom window) and a window which is vertical to the counter surface (side window), and a scanning pattern is respectively emitted from each window.
However, the multi-head scanner of the prior art has its own problems, which are explained below.
The first problem is that the apparatus usually is thick.
In Europe, the checkout operator is legally obliged to perform the job sitting down. Since the scanner is buried within a check out the counter, when the scanner is thick, a bottom of the scanner may project from the lower surface of the counter. In this case, the operator cannot accommodate his/her knees under the lower surface of the counter or manipulation flexibility of the bar code reader is deteriorated because the scanning surface becomes high, and thereby the operator's work becomes harder.
On the other hand, when an operator performs the bar code reading job while standing, such a problem may not occur. However, in some cases, a drawer is provided under the scanner to accommodate cash. In this case, when the scanner is thick, a distance from the drawer to an operator may be significant, resulting in the problem that the processing of cash may be difficult.
In light of the problem explained above, it is desirable for a scanner to have a thickness of 90 mm or less. However, actual multi-head scanners have thicknesses over 100 mm. For practical manipulation of the apparatus, a difference of thickness of about 10 mm or more is significant.
A second problem is that the multi-head scanner of the prior art is not capable of perfectly reading in 360 degrees.
A multi-head scanner preferably allows bar code reading, when the bar code is directed in any direction. That is, the scanner should be able to read the bar code information, even when the bar code is not directed to the reading window side, because the scanning patterns are emitted respectively from the bottom section and side section.
However, in the multi-head scanner of the prior art, the bar code cannot be read in some cases depending on the inclination between the bar code and the counter surface, resulting in the problem that a 360 degree reading operation cannot be assured. For example, reading is possible when the bar code is parallel to the counter surface, but reading may be impossible when the bar code is vertical to the counter surface. In this case, a perfect 360 degrees reading operation cannot be realized.
The third problem is that the multi-scanning pattern cannot be provided in some cases with a single light beam. Here, the term multi-scanning pattern is meant to represent both the scanning pattern emitted from the bottom section and the scanning pattern emitted from the side section.
In the multi-head scanner of the prior art, a plurality of light sources, for example, are provided, and the light beams from respective light sources are incident to the scanning means, such as a polygon mirror, or the like. On the other hand, the light beam emitted from a single light source is divided by a beam splitter and respective light beams are incident to the scanning means from different directions. Since the number of light beams incident to the scanning means is increased, the photo-detector for receiving the reflected light beam from the bar code and the light collecting means for inputting the reflected light beam to the photo-detector must correspond to the number of light beams. Therefore, the scanner cost may become high.
Particularly, in a shop such as a super-market, a “tray-commodity”, in which a commodity is packed on the tray, may be sold. The tray is covered with wrapping material and the bar code is attached to the wrapping material.
In the case of the prior art apparatuses, a laser scanning pattern emitted from the side section is almost parallel to the bottom window, namely such laser scanning pattern is emitted almost horizontally. Meanwhile, since the tray commodity has a problem that a fluid may leak therefrom, it is desired that the tray not be tilted at the time of reading the bar code. However, since the laser scanning pattern is emitted almost horizontally, the tray must be tilted to read the car code attached on the tray commodity. If the tray is intentionally not tilted, due to the leakage concern, a probability for non-reading of the bar code is very high because the bar code attached on the tray commodity is not irradiated with the laser scanning pattern.